Currently, various display devices are used in a variety of applications, including liquid crystal display devices. In commonly-used display devices, each pixel is composed of three subpixels for displaying three primaries of light, i.e., red, green and blue, whereby multicolor display is achieved.
However, conventional display devices have a problem in that they can only display colors in a narrow range (referred to as a “color gamut”). FIG. 40 shows a color gamut of a conventional display device which performs display by using three primaries. FIG. 40 is an xy chromaticity diagram in an XYZ color system, where a color gamut is shown by a triangle whose apices are at three points corresponding to the three primaries of red, green and blue. Also shown in the figure are plotted colors (represented by “x” symbols) of various objects existing in nature, as taught by Pointer (see Non-Patent Document 1). As can be seen from FIG. 40, there are some object colors which do not fall within the color gamut. Thus, display devices which perform display by using three primaries are unable to display some object colors.
Therefore, in order to broaden the color gamut of a display device, there has been proposed a technique which increases the number of primary colors to be used for displaying to four or more.
For example, as shown in FIG. 41, Patent Document 1 discloses a liquid crystal display device 800 each of whose pixels P is composed of six subpixels R, G, B, Ye, C and M for displaying red, green, blue, yellow, cyan, and magenta. The color gamut of the liquid crystal display device 800 is shown in FIG. 42. As shown in FIG. 42, a color gamut which is represented as a hexagonal shape whose apices are at six points corresponding to the six primary colors essentially encompasses all object colors. Thus, the color gamut can be broadened by increasing the number of primary colors to be used for displaying. In the present specification, display devices which perform display by using four or more primary colors will be collectively referred to as “multiprimary display devices”, and liquid crystal display devices which perform display by using four or more primary colors will be referred to as “multiprimary liquid crystal display devices (or simply, multiprimary LCDs)”. Moreover, conventional commonly-used display devices which perform display by using three primaries will be collectively referred to as “three-primary display devices”, and liquid crystal display devices which perform display by using three primaries will be referred to as “three-primary liquid crystal display devices (or simply, three-primary LCDs)”.
Liquid crystal display devices of the TN (Twisted Nematic) mode and the STN (Super Twisted Nematic) mode, which have conventionally been used commonly, have a disadvantage of narrow viewing angles, and various display modes have been developed for improving this.
As display modes with improved viewing angle characteristics, an MVA (Multi-domain Vertical Alignment) mode disclosed in Patent Document 2, a CPA (Continuous Pinwheel Alignment) mode disclosed in Patent Document 3, and the like are known.
The MVA mode and the CPA mode realize displaying with a high quality and a wide viewing angle. However, as a problem regarding viewing angle characteristics, a problem has newly emerged for wide-viewing-angle vertical alignment modes (VA modes) such as the MVA mode and the CPA mode; that is, the γ characteristics when observed from the front may differ from the γ characteristics when observed obliquely, i.e., a viewing angle dependence problem of the γ characteristics. The γ characteristics are the gray scale dependence of display luminance. If the γ characteristics differ between the frontal direction and oblique directions, the state of gray scale displaying will differ depending on the direction of observation, which would be especially problematic when displaying images such as photographs and when displaying TV broadcasts or the like.
A viewing angle dependence of the γ characteristics in the vertical alignment mode is visually perceived as a phenomenon where an obliquely observation results in a display luminance which is increased over the original display luminance (called “whitening”). If whitening occurs, another problem occurs in that a color which is displayed by a pixel differs between when viewed from the frontal direction and when viewed from an oblique direction.
As techniques of reducing the viewing angle dependence of the γ characteristics, a technique called multi-pixel driving has been proposed in Patent Document 4 and Patent Document 5. In this technique, one subpixel is divided into two regions, and different voltages are applied to the respective regions, thereby reducing the viewing angle dependence of the γ characteristics.